Where is ''directory WORK''? I can't see....this directory
Well your "work" directory is wherever you executed the "bedbg -prepare" command from - I am not sure where you ran this command, so its hard to tell where it is.
However, if you are in that directory, try typing:
pwd
It should print the current working directory, and try copying cellftp.self there.
Depends on the game really - you may need to alter any "dev_bdvd" references to "app_home" inside the SELF's. Furthermore some may have multiple executables that load one another.
It depends on the game - pick one and post a file list here, and we can go through it! Some games will have a tiny EBOOT.BIN and have it load say a "game.self", which also needs to be decrypted and modified.